The present invention relates to a new and improved method of, and testing apparatus for, testing the tooth flank profile of large diameter gears.
Generally speaking, the method for testing the tooth flank profiles of gears of large diameter, comprises the utilization of a testing apparatus having two contact or support elements and a measuring feeler. The measuring feeler is movable along a X-axis which is parallel to the line connecting both of the contact elements and along a Y-axis extending transverse to the X-axis. The contact elements can be placed into respective tooth gaps or spaces of a gear which is to be measured. The testing apparatus or machine is placed into a position where both axes are located in a plane which is normal to the gear axis, so that there is determined the origin or null point of a X-Y-coordinate system formed by both axes. Thereafter, the measuring feeler is moved along at least one of the tooth flanks and the thereby measured coordinates are compared with reference values.
The testing machine or apparatus of the invention, useful for performance of such method, comprises two contact slides or carriages, which can be displaced in relation to one another along a guide means extending tangentially with respect to the gear and each contact slide supports a respective contact element suitable for engagement into a tooth space or gap. Further, there is provided a cross-slide arrangement, which supports a measuring feeler or probe and comprises a X-slide or carriage, displaceable along a X-guide arrangement likewise extending tangentially with respect to the gear, and a Y-slide which is displaceable along a Y-guide arrangement or guide extending radially with respect to the gear.
In the context of this disclosure, under the expression "large diameter gears" or equivalent terminology, there is meant, in the first instance, straight and helical-toothed spur gears beginning with about 300 millimeters diameter, which because of their size cannot, or at best only with great difficulty, perform generating movements with the requisite accuracy for testing their tooth flank shape or profile, especially their more or less exact involute-shaped tooth profile.
For quite some time there exists the need of testing the shape of tooth flanks of such gears, in a simple manner with a movable test machine, either directly at a tooth flankcutting or production machine or at the site of employment of the geras. Thus, from the publication "Werkstatt und Betrieb" 1960, Vol. 5, pages 247-248, there is disclosed a method of the described type wherein there are engaged or received an uneven number of teeth between two spherical contact or support elements which can be placed into a respective tooth space or gap of a gear which is to be checked or tested. Prior to the start of the actual testing operation, the measuring feeler or probe, which likewise possesses a spherical feeler head, is centrally adjusted or set in relation to both of the contact elements such that the center of the feeler head coincides with the center line of the tooth which is to be tested. In this position there is set to null a measuring screw provided for shifting the measuring feeler along the Y-axis. After this reference setting the measuring feeler is brought into one of both neighboring tooth spaces or gaps and adjusted in the direction of the tooth base through a value corresponding to a computated elevation value at an appropriate point of the tooth flank near to the pitch circle. Then, the measuring feeler is displaced, by means of a further measuring screw in the direction of the X-axis, to such an extent until the measuring head contacts the tooth flank at the predetermined elevation or height and a dial gauge, indicating the deflections or movements of the measuring feeler, reaches its null position. Now also the measuring screw, provided for the movements along the X-axis, is set to null. From this starting position the measuring feeler is successively set to a number of likewise previously selected or computated Y-values, and following each setting along the X-axis is displaced along the tooth flank until the dial gauge indicates a null reading. A comparison of the magnitudes, through which the measuring feeler has been displaced along the X-axis, with computated X-axis values, enables recognition of possible errors in the tooth profile.
This heretofore known testing method leads to unsatisfactory results if the gear to be tested, as is conventional practice at the present time, is not or only inaccurately ground at its tooth tip surface. In this case, it is not possible by scanning a tooth tip or addendum, to obtain a sufficiently exact reference point.